
Time Travel


Classroom Activity

Objective
To help students better understand the nature of time.
 copy of "Measuring Time" student handout
(HTML)
Have students do each of the activities outlined on the "Measuring Time" student handout.
How Long Have You Lived?
Students will plot their ages, and the ages of others, on a timeline and calculate what percent of their total life each person has lived (based on average life expectancies). Have students compare the percent of male and female time living at younger versus older ages on their timelines. What do they notice about the percents?
How Long Is a Minute?
Students will use a stopwatch to see how long other
people think one minute is. You may want to have
students do this activity themselves before and after they do the experiment with others to see whether their own perception of time changes.
Time Paradox
First discuss the implications of the grandfather
paradox with students. Then have students develop their own scenarios where they go back in time and change something and have them list the many ways they think their change might affect a future timeline.
How Long Have You Lived?
Percents will differ for males and females. In the
examples given:
males living until 73year life expectancy 
females living until 80year life expectancy 
(current age) / (life expectancy) X 100 = (percent of life lived)
i.e. 11 year old male / 73 = 15% 
11 years old = 15 percent  11 years old = 14 percent 
40 years old = 55 percent  40 years old = 50 percent 
70 years old = 96 percent  70 years old = 88 percent 
90 years old = 123 percent  90 years old = 113 percent 
How Long Is a Minute?
Students may be surprised to find a wide variability in how long people think a minute is. Encourage students to look for correlations in age, gender, and other variables.
Time Paradox
Students may think that smaller changes, such as taking something like a book, may not have as big of an impact as stopping someone from being assassinated. But this can be misleading. The book removed by the time traveler may have been the inspiration for a modern invention that greatly affected society, or the precursor to a new line of scientific thought. Just the presence of an observer can affect the timeline, such as the time traveler who, by just being in a certain place, causes an accident in which someone dies or otherwise changes the course of her life.
Books
Hawking, Stephen W. "A Brief History of Time: From the Big Bang to Black Holes."
New York: Bantam Books, 1988.
Describes what we know of the universe and includes
discussions on space and time and the direction of time.
Nahin, Paul J. Time Machines: "Time Travel in Physics, Metaphysics, and Science Fiction."
New York: SpringerVerlag, 1999.
Explores time and space, time travel, and some of the paradoxes involved in time travel. The author examines the science and science fiction of many popular ideas.
Sagan, Carl. "Contact."
New York: Simon and Schuster, 1985.
This is a fictional account of looking for evidence of life other than on Earth and describes the physics involved in making such a journey.
Web Sites
NOVA Online  Time Travel
http://www.pbs.org/nova/time/
Includes text and audio from Carl Sagan about subjects ranging from wormholes to the nature of time, an excerpt from a book by an author who claims time travel is possible, a dictionary of words and concepts scientists use when discussing time travel, and an interactive game that encourages players to "think like Einstein."
Everything You Always Wanted to Know About Time Travel
http://www.biols.susx.ac.uk/home/John_Gribbin/Time_Travel.html
Provides background information on time and the
universe and the possibility of time travel.
Time Travel: Fact or Fiction?
http://math.ucr.edu/home/baez/physics/Relativity/GR/time_travel.html
Describes the problems and paradoxes of time travel.
The "Measuring Time" activity aligns with the following National Science Education Standards:
Grades 58

Mathematics Standard 3:
Mathematics as Reasoning



Mathematics Standard 7:
Computation and Estimation



Mathematics Standard 8
Patterns and Functions


Grades 912

Mathematics Standard 3:
Mathematics as Reasoning


